OOS 50-1: Effects of burn season on reproductive success of grasses in longleaf pine (Pinus palustris Miller) sandhills of North Florida

Post-fire flowering is considered an adapted trait of some plants in fire-prone ecosystems. In longleaf pine sandhills of Florida, plants likely evolved under frequent (2-8 yr), lightning-season burns (May-August) and may require a fairly specific time-of-burn to elicit flowering and seedling recruitment. Our research experimentally tested the effects of burn season on percent flowering, seedling recruitment, and germination of six grasses characteristic to longleaf pine sandhills of Northwest Florida. Five treatments with 5-7 replicate sites per treatment were randomly chosen from sandhills that had been chronically (1-6 yr) burned over the last two decades. Treatments were previous spring burns (spring 2004), winter-season burns (February 2005), current-year spring burns (April 2005), and lightning-season burns (May and July 2005). In the fall of 2005, the number of flowering culms for ten randomly chosen plants of each species at each replicate site were counted and collected for determination of floret and seed production and germination. Results suggest that flowering percent and reproductive potential are species-specific, although 4 of 6 grass species included in this study produced greater percent flowering in May and July burns, respectively. Likewise, floret and seed production followed trends similar to flowering results, with greater production in 3 of 6 grasses burned in May and July. Curiously, an endemic grass in this community showed dramatic declines in flowering and seed production as a result of May 2005 and lightning-season burns. Lightning-season burns may facilitate seed production and collection for use in ground cover restoration of longleaf pine sandhills.